584 Bulletin 167 



TABLE 73. OPTIMUM REACTION 



Strain 

 Ps. alba, 



Ps. fluorescens, — 7.3 



Ps. longa, 

 Ps. mesenterica, 

 Ps. tenuis, 



Ps. putrida, — 11.0 — 7.3 



CXII, 

 CXV, 1 

 CXL, 



CXLV, — 7.3 2 



CXLVIII, 

 XXXVI, 

 LI, 



1 No growth at 24 hours. 

 8 Trace of growth. 



7. Vitality on culture media. — Long vitality on culture 

 media was characteristic. Five month agar cultures completely 

 dried down, developed promptly with fluorescence when trans- 

 ferred to nutrient broth. 



8. Temperature relations; thermal death point. — Thin walled 

 tubes of uniform thickness with an inside diameter of 15 to 17 

 ram. were chosen for the determinations of the thermal death 

 point. Seven cc. of bouillon, -f-10 Fuller's scale, were employed 

 in each case. The inoculations were made from young broth 

 cultures, care being taken not to wet the tube above the surface 

 of the medium. In the preliminary determinations the tubes 

 were deeply submerged in the thermal bath for 10 minutes at the 

 following temperatures: 44.5, 47.7, 54.5, 58.4, 61. 3 C. After 

 exposure the tubes were incubated at 25 ° C. In this way the 

 thermal death point for all strains was roughly fixed between 

 47.7 and 54.4 C. None grew after exposure at 54.5 ° C. 



In subsequent trials the temperature of the bath was varied 

 so as to determine the death point more closely. A very large 



